yes, i agree that it is vacumn related. i tested last night by turning key on, but not starting car. sure enough, what i assume is the vac pump fires every minute or so for about 2 seconds. it is a faint "bbbuuuuuuzzzzzzzz". the door locks still function.

it would make sense to me that it pulls a vac, loses vac pressure, and fires again repeatedly trying to maintain a vacumn pressure.

i think it has to be a vac sys "leak". this is my 3rd MBwith vac , and i have never seen (read heard) this before. it's not awful or terribly loud, but i want to fix the problem to maintain my sanity. it's not a problem that i could "live with".

i will investigate more today in the light of day. any insights greatly welcomed.